Seismic Isolation of An Ammonia Tank in Turkey Through Pendulum Isolators

Abstract eng:
The paper describes the seismic isolation system for an ammonia tank located in Samsun, Turkey, an area characterised by high seismicity; the PGA values for Design Basis Earthquake (DBE-475 years return period) and Maximum Credible Earthquake (MCE-2475 years return period) are 0.278 g and 0.490 g, respectively. The supporting structure was already existing, thus one of the design criteria for the isolation system has been the reduction of base shear to a value lower than the elastic limit of the supporting structure. In effects, a response modification factor equal to one has been considered at all design level earthquakes, including MCE, due to the criticality of the structure. The seismic isolation system includes three types of double concave curved surface sliders (or friction isolation pendulums with two primary concave sliding surfaces) characterized by equivalent radius of curvature of 4.5 m, seismic vertical load capacity ranging from 1840 to 3100 kN, and ± 450 mm displacement capacity. In total there are 121 isolators. The average dynamic friction coefficient guaranteed by such isolation system is 6.2 %. The preliminary design of the isolation system has been carried out through nonlinear time history analyses on a simplified 3 masses model representing the impulsive and convective modes of vibration of the tank-liquid system, as well as the tank structure. Three couples of ground motion records have been used for such analyses, in particular Erzincan 1992, Kocaeli 1999 (Izmit station), amd Duzce 1999, properly scaled to respect the compatibility with the design spectrums (DBE and MCE). Peak values of the response parameters were used for design. The maximum base shear obtained from the analyses is 8.4% of the seismic weight at DBE, while the maximum displacement is 359 mm at MCE. Type Tests on two isolators per type have been carried out according to EN 15129, with some slight changes required by the Client. Additionally, two factory production control tests have been carried out, in order to check at least one isolator every 20 identical units. In total, 8 isolators have been tested.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket